The present application is based on Japanese patent application No. 2000-329477, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
This invention relates to a grommet of the type which forms an air layer (closed space) therein to enhance a noise-insulating effect.
2. Description of the Related Arts
One known grommet of this type is disclosed in JP-A-9-289723. FIGS. 5A to 5D are cross-sectional views showing the construction of the grommet, disclosed in this publication, and the process of mounting it on a panel.
This grommet G1, shown as the first conventional example, includes a larger-diameter tubular portion 1, having a fitting groove (fitting portion) 2 formed in its outer peripheral surface so as to fit on a peripheral edge of a through hole Pa in the panel P, a smaller-diameter tubular portion 3 for passing a wire (wire harness) W, passing through the panel through hole Pa, therethrough, a shield wall 4, which interconnects an axially-intermediate portion of the smaller-diameter tubular portion 3 and a distal end of the larger-diameter tubular portion 1 to close a space between the larger-diameter tubular portion land the smaller-diameter tubular portion 3, and is elastically deformable so as to displace the smaller-diameter tubular portion 3 in the axial direction relative to the larger-diameter tubular portion 1, an annular noise-insulating wall 5, which is disposed closer to a proximal end 3b of the smaller-diameter tubular portion 3 than the shield wall 4 is, and extends radially outwardly perpendicularly from an outer peripheral surface of the smaller-diameter tubular portion 3, and an annular engagement projection 9 formed on an inner peripheral surface of the larger-diameter tubular portion 1 at a proximal end thereof.
For using this grommet G1, first, the wire harness W is passed through the smaller-diameter tubular portion 1, and then the wire W is passed through the panel through hole Pa as shown in FIG. 5A. Then, by pulling the wire W, a distal end 3a of the smaller-diameter tubular portion 1 is passed through the panel through hole Pa, and the larger-diameter tubular portion 3, connected to the shield wall 4, is brought into engagement with the peripheral edge of the panel through hole Pa, as shown in FIG. 5B. In this condition, when the wire W is further pulled, the shield wall 4 is stretched in the axial direction, with its inner peripheral portion pulled by the smaller-diameter tubular portion 3, and the larger-diameter tubular portion 1 is pulled by the shield wall 4, so that the fitting groove 2 becomes fitted on the peripheral edge of the panel through hole Pa, as shown in FIG. 5C. At this time, the smaller-diameter tubular portion 3 is displaced forward relative to the larger-diameter tubular portion 1 because of the deformation of the shield wall 4, and therefore an outer peripheral edge 5a of the noise-insulating wall 5, formed on the outer peripheral surface of the smaller-diameter tubular portion 3 at the proximal end 3b thereof, is forced through the annular engagement projection 9 to enter the interior of the larger-diameter tubular portion 1.
When the noise-insulating wall 5 thus enters the interior of the larger-diameter tubular portion 1, with the fitting groove 2 in the larger-diameter tubular portion 1 fitted on the peripheral edge of the panel through hole Pa, the application of the pulling force to the wire W is canceled. As a result, the smaller-diameter tubular portion 3 is returned toward its original position because of the restoring action of the shield wall 4 as shown in FIG. 5D, and the outer peripheral edge 5a of the noise-insulating wall 5 is engaged with the engagement projection 9 formed on the inner peripheral surface of the larger-diameter tubular portion 1, so that a closed space 7, in which the air is filled, is formed between the noise-insulating wall 5 and the shield wall 4. As a result, the noise-insulating ability of the grommet G1 is enhanced.
The type of grommet G2 as shown in FIGS. 6 and 7 is also known as another conventional example.
The grommet G2, shown as the second conventional example, includes a larger-diameter tubular portion 11, having a fitting groove 12 for a panel through hole, a smaller-diameter tubular portion 13 for passing a wire W therethrough, a shield wall 14, interconnecting the larger-diameter tubular portion 11 and the smaller-diameter tubular portion 13, and an annular noise-insulating wall 15 integrally connected at its outer peripheral edge 15a to an inner peripheral surface of the larger-diameter tubular portion 11. An inner peripheral edge 15b of the noise-insulating wall 15 is held in intimate contact with the outer peripheral surface of the wire W passed through the smaller-diameter tubular portion 13, thereby forming an air-filled, closed space 17 between the noise-insulating wall 15 and the shield wall 14.
In the first conventional grommet G1, the annular engagement projection 9 is formed on the inner peripheral surface of the larger-diameter tubular portion 1, and the outer peripheral edge 5a of the noise-insulating wall 5, formed on and projecting from the smaller-diameter tubular portion 3 in the direction perpendicular to the axis thereof, is engaged with the engagement projection 9, thereby forming the closed space 7 for noise-insulating purposes. However, in order that the final shape with the closed space 7, shown in FIG. 5D, can be maintained, the engagement projection 9 and the noise-insulating wall 5 need to have a certain degree of rigidity. Namely, the grommet G1 is of such a construction that the noise-insulating wall 5 is held in intimate contact with the engagement projection 9 by the restoring force of the shield wall 4 so as to maintain the noise-insulating ability, and therefore the noise-insulating wall 5 and the engagement projection 9 must be kept in the mutually-engaged condition against this restoring force.
Since the noise-insulating wall 5 and the engagement projection 9 have the increased rigidity, a large force is required in the process from the step of FIG. 5B to the step of FIG. 5C, that is, in the process of insertion of the noise-insulating wall 5 into the larger-diameter tubular portion 1 through the engagement projection 9, and this invited a problem that the noise-insulating wall 5 could not be easily inserted into the larger-diameter tubular portion 1.
In contrast, it may be proposed that the engagement projection 9 and the noise-insulating wall 5 are decreased in rigidity so as to reduce the inserting force. In such a case, however, the engagement projection 9 and the noise-insulating wall 5 can be easily disengaged from each other, and when this disengagement occurs, the air layer is lost, which leads to a possibility that the noise-insulating ability is not maintained.
And besides, in the final shape of FIG. 5D, the noise-insulating wall 5 is pressed against the engagement projection 9 (in order to positively maintain the intimate contact therebetween) by the restoring force of the shield wall 4, and therefore the smaller-diameter tubular portion 3 is not completely returned to its initial position, and there was encountered a problem that the dimension from the fitting groove 2 to the distal end of the grommet G1 before mounting the grommet on the panel P as shown in FIG. 5A was different from the dimension after mounting the grommet on the panel P as shown in FIG. 5D. Namely, the dimension a before mounting the grommet is increased to the dimension b after mounting the grommet. As a result, the wire W can not be mounted accurately in a predetermined position.
The second conventional grommet G2, shown in FIGS. 6 and 7, has no problem in so far as it is used in its original shape. However, in the case where the proximal end portion of the smaller-diameter tubular portion 13 is extended so as to increase a holding force for holding the wire W, or in the case where a filling cup portion 18 for being filled with a water-stopping material is further formed at the proximal end of the thus-extended smaller-diameter tubular portion 13, there is encountered a problem from the viewpoint of the production.
Namely, for forming the air layer (closed space 17), the production must be effected in such a manner that the inner peripheral edge 15b of the noise-insulating wall 15 is held in intimate contact with the outer peripheral surface of the smaller-diameter tubular portion 13. However, it is impossible to form such a configuration from the viewpoint of molding (from the viewpoint of removal of the molded product). Therefore, from a structural point of view, it is impossible to extend the proximal end portion of the smaller-diameter tubular portion 13 while providing the noise-insulating wall 15, and it was impossible to apply the technique of FIGS. 6 and 7 to the type of grommet in which the water-stopping material was filled.
In view of the foregoing, it is an object of this invention to provide a grommet which can solve the following problems.
(1) A noise-insulating wall can be inserted into a larger-diameter tubular portion with a small inserting force so as to form an air layer (closed space) for noise-insulating purposes.
(2) The noise-insulating wall, once inserted in the larger-diameter tubular portion, can be prevented from being withdrawn therefrom, thereby positively maintaining a noise-insulating effect.
(3) The position of a smaller-diameter tubular portion relative to the larger-diameter tubular portion after setting the grommet in a panel through hole will not much differ from that before setting the grommet in the panel through hole, so that a wire can be held in a predetermined position.
(4) The invention can be applied to the type in which a water-stopping material is filled.
According to the present invention there is provided a grommet characterized by the provision of:
a larger-diameter tubular portion having a fitting portion for fitting on a peripheral edge of a panel through hole;
a smaller-diameter tubular portion for passing a wire, passing through the panel through hole, therethrough;
a shield wall which interconnects an axially-intermediate portion of the smaller-diameter tubular portion and the larger-diameter tubular portion to close a space between the larger-diameter tubular portion and the smaller-diameter tubular portion, and is elastically deformable so as to displace the smaller-diameter tubular portion in an axial direction relative to the larger-diameter tubular portion; and
a noise-insulating wall which is disposed closer to a proximal end of the smaller-diameter tubular portion than the shield wall is, and is flaring into a conical wall-shape in a direction of extending of the proximal end of the smaller-diameter tubular portion, and is joined at its inner peripheral edge to an outer peripheral surface of the smaller-diameter tubular portion, wherein when the smaller-diameter tubular portion is displaced relative to the larger-diameter tubular portion in a direction toward its distal end, an outer peripheral edge of the noise-insulating wall, provided as a free edge, is brought into sliding contact with an inner peripheral surface of the larger-diameter tubular portion, and in this condition, when the displacement is canceled, the outer peripheral edge is engaged with the inner peripheral surface of the larger-diameter tubular portion, so that the noise-insulating wall is reversed on its inner peripheral edge to be formed into a conical wall-shape whose direction is reverse to that of its initial shape, thereby forming a closed space between the noise-insulating wall and the shield wall.
For using this grommet, first, the wire is passed through the smaller-diameter tubular portion, and then the wire is passed through the panel through hole. Then, the wire is pulled, thereby passing the distal end of the smaller-diameter tubular portion through the panel through hole, and at the same time the larger-diameter tubular portion, connected to the shield wall, is brought into engagement with the peripheral edge of the panel through hole. In this condition, when the wire is further pulled, the shield wall is deformed in the axial direction, with its inner peripheral portion pulled by the smaller-diameter tubular portion, and the larger-diameter tubular portion is pulled by this shield wall, so that the fitting portion of the larger-diameter tubular portion becomes fitted on the peripheral edge of the panel through hole. At this time, the smaller-diameter tubular portion is displaced forward relative to the larger-diameter tubular portion because of the deformation of the shield wall, and therefore the outer peripheral edge of the noise-insulating wall, formed on the outer peripheral surface of the smaller-diameter tubular portion at the proximal end portion thereof, enters the interior of the larger-diameter tubular portion while this outer peripheral edge is held in sliding contact with the inner peripheral surface of the larger-diameter tubular portion. At this time, the noise-insulating wall has the conical wall-shape tapering in the direction of insertion of this wall into the larger-diameter tubular portion (that is, the direction of the conical wall-shape of the noise-insulating wall is the forward direction, i.e., the direction of insertion of this wall into the larger-diameter tubular portion), and therefore the noise-insulating wall can be easily inserted into the larger-diameter tubular portion with a small force without producing a large catching resistance.
When the noise-insulating wall thus enters the interior of the larger-diameter tubular portion, with the fitting portion of the larger-diameter tubular portion fitted on the peripheral edge of the panel through hole, the application of the pulling force to the wire is canceled. As a result, the smaller-diameter tubular portion is returned to its original position because of the restoring action of the shield wall, and the noise-insulating wall, which is retained at its outer peripheral edge by the larger-diameter tubular portion, is reversed on its inner peripheral edge to be formed into the conical wall-shape whose direction is reverse to that of its initial shape, thereby forming the closed space between this noise-insulating wall and the shield wall. This closed space functions as an air layer isolated from the exterior, so that the noise-insulating ability of the grommet is enhanced.
In this condition of use, in order that the outer peripheral edge of the noise-insulating wall can be disengaged from the larger-diameter tubular portion, the noise-insulating wall need to be reversed to be returned to its initial conical wall-shape. However, the noise-insulating wall, once reversed to be brought into the engaged condition, will not be easily returned to its initial conical wall-shape since its outer peripheral edge is retained by the larger-diameter tubular portion, and therefore this noise-insulating wall will not be easily disengaged from the larger-diameter tubular portion. Therefore, the air layer can be positively maintained, and the high noise-insulating effect can be secured.
The noise-insulating wall will not be easily disengaged from the larger-diameter tubular portion because of its shape, and therefore the rigidity of the noise-insulating wall can be decreased, and therefore the noise-insulating wall can be more easily inserted into the interior of the larger-diameter tubular portion. Namely, the grommet can be mounted with a small force.
The noise-insulating wall, when reversed from the initial shape, is formed into the conical wall-shape tapering in the direction of returning of the smaller-diameter tubular portion to the initial position (that is, the direction of the conical wall-shape of the reversed noise-insulating wall is the forward direction with respect to the direction of returning of the smaller-diameter tubular portion to the initial position), and therefore the smaller-diameter tubular portion can be returned to its original position without hardly receiving a push-back resistance from the noise-insulating wall. Therefore, the smaller-diameter tubular portion can be properly returned to its initial position, so that the dimension of the grommet before setting it on the panel will not substantially differ from the dimension after setting it on the panel. And besides, the noise-insulating wall, reversed into the conical wall-shape whose direction is reverse to that of its initial shape, is held in intimate contact with the inner peripheral surface of the larger-diameter tubular portion by its own restoring force, so that the air-tightness of the closed space is positively maintained.
The noise-insulating wall is formed integrally on the outer peripheral surface of the smaller-diameter tubular portion, and is formed into the outwardly-spreading conical wall-shape, and therefore even when the filling cup portion for the water-stopping material is provided at the proximal end of the smaller-diameter tubular portion, the grommet can be easily produced by a molding operation using a mold.
In the grommet of the invention, the outer diameter of the noise-insulating wall in its free condition before the reversing thereof is larger than the diameter of the inner peripheral surface of the larger-diameter tubular portion with which the outer peripheral edge of the noise-insulating wall can be brought into sliding contact.
In this grommet, the outer diameter of the noise-insulating wall is larger than the inner diameter of the larger-diameter tubular portion, and therefore the force of intimate contact of the noise-insulating wall with the inner peripheral surface of the larger-diameter tubular portion can be increased.
In the grommet of the invention, an engagement portion for retaining the outer peripheral edge of the noise-insulating wall is provided at the inner peripheral surface of the larger-diameter tubular portion.
In this grommet, the outer peripheral edge of the noise-insulating wall is positively engaged with the engagement portion, and therefore will not be easily disengaged therefrom.
In the grommet of the invention, a cylindrical tubular portion, which can be brought into surface-to-surface contact with the inner peripheral surface of the larger-diameter tubular portion to be frictionally engaged with this inner peripheral surface, is formed at the outer peripheral edge of the noise-insulating wall.
In this grommet, the cylindrical tubular portion for frictional engagement with the inner peripheral surface of the larger-diameter tubular portion is provided at the outer peripheral edge of the noise-insulating wall, and therefore the area of intimate contact between the noise-insulating wall and the larger-diameter tubular portion is increased.
In the grommet of the invention, the shield wall is formed into a conical wall-shape tapering toward the proximal end of the smaller-diameter tubular portion, and can be reversed on its outer peripheral edge in such a manner that the direction of its conical wall-shape is reversed, thereby allowing the displacement of the smaller-diameter tubular portion, and the smaller-diameter tubular portion is returned to its initial position by a restoring force of the shield wall which restores it into its initial shape, thereby reversing the noise-insulating wall.
In this grommet, the smaller-diameter tubular portion is returned into its initial position by the strong reversing restoring force of the shield wall produced when this shield wall, brought into the reversed condition by pulling the wire, is restored into its initial shape. Therefore, when the application of the pulling force to the smaller-diameter tubular portion is canceled, the smaller-diameter tubular portion is returned into its initial position by the strong force, and at this time the noise-insulating wall is pulled by the smaller-diameter tubular portion, and is reversed in one breath, thereby forming the closed space. Namely, the strong reversing restoring force of the shield wall can be effectively utilized for reversing the noise-insulating wall, and therefore after the wire is pulled to a certain degree to apply the force to the grommet, this pulling is canceled, and merely by doing so, the grommet can be automatically mounted in the proper condition.
In the grommet of the invention, a filling cup portion for being filled with a water-stopping material, which fills in interstices in the wire passing through the smaller-diameter tubular portion, is formed at the proximal end of the smaller-diameter tubular portion, the filling cup portion being larger in diameter than the smaller-diameter tubular portion.
In this grommet, the interstices in the wire can be sealed by the molten water-stopping material charged into the filling cup portion, and therefore the water-stopping ability can be enhanced.
In the grommet of the invention, the noise-insulating wall extends continuously from an outer peripheral edge of a conical wall forming a bottom surface of the filling cup portion.
In this grommet, the noise-insulating wall extends continuously from the outer peripheral edge of the conical wall forming the bottom surface of the filling cup portion, and therefore as compared with the case where the noise-insulating wall is provided separately from the filling cup portion, the axial dimension of that portion of the smaller-diameter tubular portion, including its proximal end, can be reduced.